ENVIRONMENTAL PEANUT ALLERGEN LEVELS LOWER THAN SUSPECTED

Because of its severity, peanut allergy frequently causes patients and their families to limit their activities to avoid exposure to peanuts. However, a study by Perry et al suggests that many of these limitations are not necessary: The researchers were unable to detect levels of airborne allergen in environments simulating public eating places, airplanes, and sporting events—places where peanuts are usually present. Furthermore, they found that most surfaces contaminated with peanut allergen can be cleaned relatively easily.

Nineteen adult volunteers without peanut allergy consumed various types of peanut products in a manner designed to simulate common situations. For example, they ate peanut butter sandwiches to simulate a school cafeteria, and they shelled and ate roasted peanuts (and were asked to walk on the shells) to simulate a sports arena. Air samples were collected from the areas immediately around the volunteers and from sites up to 10 feet away. The volunteers also cleaned smeared peanut butter off their hands using different cleaners.

Additionally, table surfaces had been tested after peanut butter was wiped off using various cleaners. Furthermore, peanut allergen (Ara h 1) levels were measured on tables and surfaces at six participating schools.

Most cleaners effectively removed all traces of Ara h 1 from tabletops and hands. During the simulations, levels of airborne allergen were not detectable—even though peanut exposure far exceeded that which would normally be encountered. Perry et al acknowledge the possibility that during the simulations some airborne peanut allergen may have been present, but it was below the detection threshold of the assay used.

In the six schools tested, no food preparation areas or desktops had detectable levels of Ara h 1. However, Ara h 1 was found on one of 13 water fountains tested, at a level of 130 ng/mL.

The authors noted that ideally a similar study should be performed challenging patients with peanut allergy in these simulated settings. Nevertheless, they found that the risk of exposure to peanut allergen is relatively low in the environment if surfaces and hands are cleaned properly.

Perry TT, Conover-Walker MK, Pomés A, et al. Distribution of peanut allergen in the environment. J Allergy Clin Immunol. 2004;113:973-976.

IMMUNOTHERAPY USING HOUSE DUST MITE ALLERGEN CONFERS SLIGHT BENEFIT

House dust mite is a common indoor allergen and asthma trigger. Recently, Maestrelli et al conducted a randomized, double-blind, placebo-controlled trial to determine if house dust mite–specific immunotherapy affected asthma medication use and lung function. Their findings showed that immunotherapy had a marginally significant effect that could be attributed to a decrease in the allergic response.

The study included 72 patients with a history of asthma and sensitization to house dust mite. Patients were observed for one year before the study; they were then randomized to receive either immunotherapy or placebo. In addition, they were given instructions on allergen avoidance, along with allergen-impermeable mattress and pillow covers.

An extract containing both Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1) allergens was used for immunotherapy. Clinical assessments were performed at baseline and then every three months for three years. Patients also underwent skin tests at baseline and yearly thereafter.

The levels of house dust mite allergen in patients’ homes did not change during the study. Immunotherapy was associated with significantly less skin sensitivity to the allergen, whereas in the placebo recipients there was a trend toward increasing skin sensitivity.

Peak expiratory flow (PEF) values improved significantly in the immunotherapy group but were unchanged in the placebo recipients. During the third year of treatment, patients’ use of bronchodilators in autumn decreased significantly in the treatment group. The improvement in PEF was similar to that seen in a study using low-dose budesonide.

The authors observed that immunotherapy with house dust mite allergen provided small but significant benefits when used with traditional asthma care. They cautioned that immunotherapy should not be used in patients with severe asthma because of safety risks.

Maestrelli P, Zanolla L, Pozzan M, Fabbri LM. Effect of specific immunotherapy added to pharmacologic treatment and allergen avoidance in asthmatic patients allergic to house dust mite. J Allergy Clin Immunol. 2004;113:643-649.

ICU ADMISSIONS UP, OUTCOMES BETTER IN HIV PATIENTS

Although the use of highly active antiretroviral therapy (HAART) in HIV-infected patients has drastically reduced the number of hospital admissions for HIV-associated disorders, HAART’s effect on ICU admissions has not been assessed. To investigate this issue, Narasimhan et al compared the characteristics of HIV-infected patients admitted to the ICU of a large urban hospital during two separate periods: the first six months of 2001 and the months between November 1991 and October 1992. The researchers found that ICU admissions were more frequent in 2001 than in the earlier period, but non–HIV-related conditions were usually the cause.

During the first six months of 2001, 53 HIV-infected patients had a total of 63 ICU admissions. During the year ending in October 1992, 65 HIV-infected patients were admitted to the ICU. Patients in 2001 were more likely to have acquired HIV from injection drug use. Twenty-eight patients in 2001 were receiving HAART; in comparison, only 22 patients had been given any type of antiretroviral therapy in 1991–1992.

In both periods studied, the most common reason for ICU admission in HIV-infected patients was respiratory failure, but the frequency was lower in 2001 than in 1991–1992 (22% vs 54%, respectively). Two thirds of the ICU admissions in 2001—but only 12% of ICU admissions in the earlier period—were for reasons unrelated to HIV infection.

Survival to hospital discharge was significantly higher in 2001 than in 1991–1992 (71% vs 49%, respectively). Serum albumin level was the only laboratory measurement inversely correlated with survival in 2001.

Contrary to what the investigators had originally hypothesized, post-HAART patients had increased ICU admissions, knew that they were seropositive, and had very different types of health disorders and outcomes than did patients treated before the widespread use of HAART.

Narasimhan M, Posner AJ, DePalo VA, et al. Intensive care in patients with HIV infection in the era of highly active antiretroviral therapy. Chest. 2004;125:1800-1804.

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